Secure keyboard with random order of key interrogation

Abstract

A keyboard arrangement, such as for a computer or the like, has a number of keys arranged in rows and columns. The keys of each row are associated with a respective conductor and the keys of each column are associated with a respective conductor. Each key, when depressed, interconnects the two conductors. An interrogator is provided to interrogate the rows respectively by transmitting pulses to the rows and to interrogate the columns, to determine the presence of a transmitted pulse. The interrogator is adapted to interrogate the rows in a random or quasi-random order during successive cycles of operation.

What is claimed is: 
     
       1. A keyboard arrangement comprising a plurality of keys arranged in rows and columns, said rows of keys being associated with a respective first set of conductors and said columns of keys being associated with a respective second set of conductors, each key acting, on depression thereof, to interconnect respective ones of said first and second sets of conductors associated with the row and column in which the key is located; means for interrogating said rows during each of a plurality of cycles of operation by transmitting pulses to said rows to determine the presence of a transmitted pulses on any one of said columns, the interrogating means being adapted to interrogate said rows and columns in a random or quasi-random order during successive cycles of operation. 
     
     
       2. An arrangement according to claim 1 wherein a random number generator is provided to determine the random order of row interrogation. 
     
     
       3. An arrangement according to claim 2 wherein the random number generator generates a number identifying a row, and memory means are provided adapted to store signals representative of rows which have been scanned in any cycle of operation, the number generated by the random number generator being compared with the numbers present in said memory, the identified row being interrogated if the number generated by the random number generator is not present in said memory. 
     
     
       4. An arrangement according to claim 1 wherein a counter is provided to count the number of rows interrogated, the apparatus being adapted to continue interrogating rows until the row interrogation counter contains such a number that is indicative that all rows have been interrogated, the apparatus being adapted to then commence a further cycle of operation. 
     
     
       5. A keyboard arrangement having a plurality of cycles of operation comprising: a plurality of keys arranged in a plurality of rows and a plurality of columns;   first conductors associated with respective rows of keys;   second conductors associated with respective columns of keys, whereby depression of any given key interconnects one each of said first and second conductors;   a first interrogator for randomly interrogating one of said plurality of rows and said plurality of columns by transmitting pulses thereto during one cycle of operation;   a second interrogator for interrogating the other of said plurality of rows and plurality of columns to determine the presence of one of said transmitted pulses in said other of said plurality of rows and plurality of columns.   
     
     
       6. The keyboard arrangement of claim 5 wherein said one of said plurality of rows and plurality of columns comprises said plurality of rows. 
     
     
       7. The keyboard arrangement of claim 5 wherein said one of said plurality of rows and plurality of columns comprises said plurality of columns. 
     
     
       8. The keyboard arrangement of claim 5 further comprising a random number generator for determining a random order of interrogation for said first interrogator during successive cycle of operation. 
     
     
       9. The keyboard arrangement of claim 8 wherein said random number generator generates a number identifying a row or column to be interrogated within one of said plurality of rows and plurality of columns, and wherein the keyboard arrangement further includes a memory device adapted to store signals representing said numbers of rows or columns within said one of said plurality of rows and plurality of columns interrogated by said first interrogator during each cycle of operation, the memory device including means for comparing the identifying number with numbers present in the memory, whereby the identified row or column is interrogated by the first interrogator if the identifying number is not present in the memory. 
     
     
       10. The keyboard arrangement of claim 9 further including a counter for counting the rows or columns within said one of said plurality of rows and columns interrogated by said first interrogator. 
     
     
       11. A method for securing a keyboard against electronic eavesdropping comprising the steps of: (a) providing a keyboard having a plurality of keys arranged in a plurality of rows and a plurality of columns, and wherein first conductors are associated with respective rows of keys, and second conductors are associated respective columns of keys, such that depression of any key interconnects one each of said first and second conductors as determined by key location;   (b) interrogating one of said rows and columns of keys randomly by transmitting pulses through one of said first and second conductors associated with said one of said rows and columns, respectively, a depressed key in said one of said rows and columns causing a corresponding pulse to be transmitted in a respective one of said second and first conductors associated with a respective one of said columns and rows;   (c) interrogating one of said plurality of columns and said plurality of rows of keys to determine the presence of said corresponding pulse to thereby identify said depressed key; and   (d) relaying information regarding the identified key to a microprocessor.   
     
     
       12. The process of claim 11 wherein step (c) is carried out by providing one of a column and row latch for one of said plurality of columns and said plurality of rows, said columns and rows latch entering a latched state upon reception of one of said pulses, and interrogating said one of said plurality of column latches and said plurality of row latches to determine if a respective column and row latch has entered the latched state by receipt of said one of said pulses. 
     
     
       13. The process of claim 11 wherein step (b) is carried out by generating a random number identifying one of a row and column to be interrogated, providing a memory to store random numbers identifying said one row and column already interrogated, comparing the generated random number with the stored random numbers, and interrogating another one of said rows and columns if the generated random number is not present in the stored random numbers. 
     
     
       14. The process of claim 11 wherein steps (b) through (d) are repeated until all of said one of said plurality of rows and said plurality of columns have been interrogated. 
     
     
       15. The process of claim 11 wherein steps (b) through (d) comprise one cycle of operation, and wherein after all of said one of said plurality of rows and said plurality of columns have been interrogated, a new cycle of operation is commenced.